Manual

Table Of Contents
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Naturally, with a 16-bit input you would expect activity in bits 1-16, and with a 24-bit input
you would expect activity in bits 1-24. As noted in the introduction to this section, if there is
processing before the plug-in, you would expect ‘inters’ and activity on all bits, including bits
higher than 24 (even if it’s a 16-bit input signal).
The following diagrams show the plug-in FFT displaying the INPUT and DIFF signals with
varying degrees of dither and truncation.
First, in order to see the effect on the noise floor we input 1kHz and 2kHz tones at -60dB. As
this is a low-level signal at -60dB, there is no activity on the top ten segments of the bit-
meter.
Note the magnified scale down to -180dB. (Swipe left with the right-hand mouse button
pressed.)
5.2.1 HD-AAC
HD-AAC 24-bit dither/truncation (correct dither/truncation)
The noise floor of the input signal is displayed as around -175dB (~30dB down
from -144dB).
The diff signal is indicating -180dB (the 24-bit integer input is identical to the 24-bit integer
post-codec, with no ‘inters’).
The bit meter shows no activity in bits greater than 24.
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